I would concur that Nortons causes more trouble than it solves. At present, there are no viruses on the Mac. There are a couple of legitimate antivirus products such as Norton's, Virex and ClamAV.
I'd still say all of these are pointless and come from the insecure, Windows-generated mentality that "viruses will get into your system. You need this tool to search for them and remove them" which is a bit like saying "thieves will break into your car, so you need this baseball bat to go in there every day and chase them out".
It is a mentality that I find offensive and stupid since there is a whole industry that has sprung up around giving computer users a false sense of security. And the idea that any of these tools can simply "clean" or "fix" a system is simply insulting.
Of the three I mentioned, Norton's is the one I'd avoid the most because of the number of ways in which it hooks into the system, scanning everything in "real time" as it is written to the hard drive. This is intended to be more thorough, but in essence it just means that it can easily screw up your system.
Virex is another commercial one and I mention it because most IT departments will accept it - I'd assume you're only asking because your IT manager or boss has insisted you have antivirus software. Virex runs as a simple scan of files and searches for a selection of known Windows viruses that could, concievably, be found on a Mac. It never finds any, unless you've been letting Windows users store files on your Mac server, but it does do what it claims to do.
ClamAV is a free open-source scanner with a very comprehensive database and fast updates. I recommend it highly.
